1. Field of the Invention
This invention relates to computer systems, and more particularly, to the identification and configuration of peripheral devices coupled to a peripheral interconnect bus.
2. Description of the Related Art
As the complexity of computer technologies grows and more, improved features are available to users of personal computers, demand for these features increases. PC (personal computer) users also demand that these features be made available at a low cost. These pressures force PC designs to use higher levels of integration throughout the system. The need for a higher level of integration may lead to the development of new types of peripheral buses and I/O (input/output) concepts.
One of the subsystems which has been targeted for increased integration is the audio/modem subsystem. Integration of the audio/modem subsystem into the motherboard by physically soldering components of the subsystem to the motherboard has been problematic because of delays resulting from certification of the modem. These problems have, in part, been addressed by development of various new specifications, including the Audio Codec '97 (AC '96) and the Audio/Modem Riser (AMR) Specification developed by Intel. The AMR Specification, which in some embodiments may be partly based on the AC '97 specification, defines a hardware-scalable original equipment manufacturer (OEM) motherboard riser board and interface that supports both audio and modem functions. By physically partitioning the portion of the modem that must be certified (analog I/O) on a riser module which is separate from the motherboard, certification processes do not delay the development of the remainder of the motherboard.
Referring to FIG. 1, a typical physical configuration of an AMR card on a motherboard is illustrated. In this system, riser card 11 is plugged into an expansion slot 12 of motherboard 13. The audio/modem subsystem includes controller 14 which is mounted directly to motherboard 13, as well as codec 15 which is mounted to riser card 11. Because riser card 11 can be removed from expansion slot 12 and thereby disconnected from motherboard 13, riser card 11 can be certified without regard to motherboard 13.
While riser card 11 can be physically decoupled from motherboard 13, riser card 11 is provided and installed by the original equipment manufacturer. It is contemplated by the AMR Specification that the configuration of the audio/modem subsystem will be known and its design taken into account in the design and configuration of the motherboard, including configuration of the BIOS software. Often, however, this is not the case.
In developing the AMR Specification, it was theorized that, because end users would not change or install audio/modem riser cards themselves, there would be no need for the riser cards to be enumerated. (“Enumeration” refers to the process of identifying buses and devices coupled to the buses so that plug and play software can allocate the appropriate resources for the devices, install the appropriate drivers, etc. This process is employed, for example, to identify devices connected to PCI buses.) Consequently, it was expected that the audio/modem riser devices would be known at the time the BIOS was installed, and the BIOS could be programmed for the devices. The AMR Specification therefore provided no mechanism for identifying these devices.
While the riser cards are not typically changed or installed by end users, they are often installed at the last stage of the PC building process. Consequently, the BIOS code may have already been installed by the time the riser card is plugged into the motherboard and may not be programmed for the particular riser card that is installed. Since the riser card installation may be performed as part of a configuration-to-order process at a distribution depot, it is likely that the riser card which is actually installed is not the same one which is expected by the BIOS code.
Furthermore, due to the theory behind the AMR specification, peripheral buses based on this specification may lack flexibility. Plug and play devices may be difficult, if not impossible to support. Configuring a bus based on this specification must follow design rules that are already defined in the specification. Thus, peripheral devices having new features and functionality may be prevented from being implemented on this bus, or may only operate with reduced functionality. The bus may be unable to respond adaptively to various devices coupled to it.